Wire notification service and finalization worker into server host

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/EnvelopeFinalizationWorker.cs

@@ -0,0 +1,63 @@
+using EnvelopeGenerator.Application.PdfSigning;
+using EnvelopeGenerator.Domain.Constants;
+using EnvelopeGenerator.Infrastructure;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace EnvelopeGenerator.Server.Services;
+
+public sealed class EnvelopeFinalizationWorker(
+    IServiceScopeFactory scopeFactory,
+    ILogger<EnvelopeFinalizationWorker> logger) : BackgroundService
+{
+    private static readonly TimeSpan PollInterval = TimeSpan.FromMinutes(1);
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                using var scope = scopeFactory.CreateScope();
+                var dbContext = scope.ServiceProvider.GetRequiredService<EGDbContext>();
+                var sender = scope.ServiceProvider.GetRequiredService<ISender>();
+
+                var envelopeIds = await dbContext.Envelopes
+                    .AsNoTracking()
+                    .Where(e => e.Status == EnvelopeStatus.EnvelopeCompletelySigned && e.DocResult == null)
+                    .Select(e => e.Id)
+                    .ToListAsync(stoppingToken);
+
+                foreach(var envelopeId in envelopeIds)
+                {
+                    try
+                    {
+                        await sender.Send(new FinalizeEnvelopeCommand()
+                        {
+                            Id = envelopeId,
+                            BurnedAllowed = false,
+                            SaveDocResult = true,
+                        }, stoppingToken);
+                    }
+                    catch(Exception ex)
+                    {
+                        logger.LogError(ex, "Unexpected exception happened during finalization of envelope. Envelope ID: {EnvelopeId}", envelopeId);
+                    }
+                }
+
+                // continue here
+                logger.LogDebug("EnvelopeFinalizationWorker found {Count} signed envelope(s) without DOC_RESULT.", envelopeIds.Count);
+            }
+            catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+            {
+                break;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "EnvelopeFinalizationWorker failed while reading envelopes.");
+            }
+
+            await Task.Delay(PollInterval, stoppingToken);
+        }
+    }
+}